The present invention relates to the general field of aircraft gas turbine engines for which it is necessary for the engine to idle for a certain duration on the ground before causing the engine to be shut down completely.
In the field of aviation, it is common practice in utilization manuals for aircraft pilots to indicate that the engine needs to run at an operating speed known as “idling” for a certain duration before causing the engine to be shut down completely. This duration is referred to as “stabilizing the engine” and it is associated mainly with the risk of the oil or fuel in the engine coking on hot portions of the engine (e.g. on injectors for injecting fuel into the combustion chamber of the engine). In order to avoid excessive coking of such hot portions of the engine, it is thus recommended to leave the engine operating at an idling speed for a certain duration before shutting it down completely.
The duration of this engine stabilization stage is generally predefined as a function of the type of engine and it typically lies in the range 30 seconds to 2 minutes.
However, imposing a fixed stabilization duration presents numerous drawbacks. Specifically, if it is desired to cover the worst possible thermal situation for the engine, then the stabilization duration will necessarily be long, which imposes a waiting time that is penalizing for the crew of the aircraft before they can shut the engine down completely. In contrast, if it is desired to minimize this constraint for the crew, the stabilization duration should be as short as possible, which can expose the engine to significant coking phenomena that, in the long run, lead to significant maintenance costs and times.
There therefore exists a need for a method of determining a stabilization duration at idling speed for an aircraft gas turbine engine prior to complete shutdown that does not present the above-mentioned drawbacks that are associated with determining a fixed stabilization duration.